1. Field of the Invention
The present invention relates to an optical deflection device and an image projection display apparatus using the optical deflection device, and more particularly to an optical deflection device and an image projection display apparatus capable of performing an optical deflection operation in four directions along two axes.
2. Discussion of the Background Arts
A digital micro-mirror device including a torsion bar hinge has been proposed by L. J. Hornbeck. The digital micro-mirror device is developed into a spatial light modulator which includes a group of micro mirrors. The spatial light modulator is referred to as a DMD (digital micro-mirror device) and is used in image projection display apparatuses, for example.
In this type of background device, a mirror is usually supported by a torsion bar (i.e., a hinge). The mirror is driven by changing an electrical potential (hereinafter referred to as potential) of the mirror. A larger deflection angle can be obtained in a bi-directional operation of the mirror than in a mono-stable operation. To obtain bi-stability, a hinge of relative high stiffness is used for the mirror in the background device. In driving the mirror, therefore, the potential of the mirror and potentials of electrodes opposite to the mirror are simultaneously changed.
A device such as a spatial light modulator and an optical deflection device using a hinge has relatively high resilience due to its stiffness, and thus a driving voltage for driving the device increases up to several tens of voltages. If the stiffness is reduced to decrease the driving voltage, however, the hinge is bent and a center location of a mirror may not be maintained. To perform the bi-stable operation, therefore, a relatively complicated mechanism is necessary. For example, a tilt of the mirror is changed by changing a first potential of the mirror and the potentials of the electrodes. Further, a light is deflected only in one axial direction in the device. Accordingly, a color selecting device, such as a color wheel, may be needed.